The history of mankind is a history of migration. In the 100,000 years since our species, the homo sapiens, walked out of Africa, it had colonised every land mass in the world except Antarctica by the time civilisations began to appear. And we also facilitated extermination of all other hominid species and countless other flora and fauna during our journeys to new lands. With all the creature comforts civilisation has provided us, our drive to wander and appetite for destruction have not been abated; in fact they have gone into overdrive.
The sudden movement of half a million refugees and migrants towards the heart of Europe and Germany’s startling decision to embrace hundreds of thousands people from a far off war-torn land have dominated news cycles in the recent days. While Germany’s embrace of Syrian refugees has drawn lot of praise in international media, it has also generated wide-spread angst and trepidation among the general people of Europe. One only has to skim through comments and feedback from readers in the bastions of liberal media in the West to see the pervasive apprehension about changing demography.
Meanwhile in the USA, self-professed showman and entertainer Donald Trump has built a seemingly unassailable lead among Republican presidential hopefuls by masterfully playing the strings of demographic fear in white America. People in the West know that beyond all periodic and aperiodic political changes, demography is the destiny and demography is changing right before their eyes.
While migration from the global south to the west dominate news and analysis in global discourse, ongoing demographic change in Asia and Africa dwarfs the change in the west in magnitude and pace. Not only are there vast political and economic migrations across borders within these continents, but also huge internal migration from rural communities to cities is rapidly transforming demography and society.
Politics and economics have always been the main drivers of human migration, but the manner in which they historically interacted to continuously recreate the mélange of humankind is not yet clearly formulated. Until the mid-twentieth century, historians favoured a national entity model of mass migration, a whole tribe or ethnic group suddenly moving across vast spaces driven by economic need, political persecution at home, or lust for political conquest of new lands. This was popularly known as the billiard ball model from the way different coloured balls move from one place to another but remain intact in essence.
The excesses of hyper-nationalism in the two world wars re-oriented post-war study of migration towards a slow accretion model where small groups of vigorous and risk-taking warriors crossed boundaries into new lands and gradually developed new political order by facilitating migration of follower population and subsuming indigenous people. This is known as the snowball model; from the way snowflakes can grow into a snowball by steady accumulation.
Current scholarly opinion suggests that both models are valid to some extent, and historical migration patterns lie somewhere in between billiard balls and snowballs. But the most important consensus is that group identities like nations and political units like nation states are not successors of continuous and unalloyed traditions but current incarnation of historical entities that were being continuously transformed and re-created.
Many historians also say that like nationalism and nation-states, genocide and ethnic cleansing too are modern phenomena. Until a few hundred years ago, humanity lacked communication systems sophisticated enough to enable development of national consciousness over a large part of the population.
As a corollary, murderous hatred to a foreign population too was hard to propagate in a people as a whole. Throughout history, violent conquest of new lands usually meant elimination of the elite class as a whole, while leaving the general people largely intact. Moreover, invasion or migration of a foreign people usually meant enthusiastic admixing with the native population.
Until a couple of decades ago, historians had to depend on written records and archaeological findings to piece together a historical map of human migration, but the advent of fast and cheap gene mapping technology have now put population genetics at the centre of the study of migration. The spreading out of homo sapiens from Africa to all corners of the globe produced small but distinct genetic differences between different populations in separated places. When different groups interacted, through migration, invasion, or diffusion, the interactions produced genetic admixture among the DNA of the offspring. After the interaction period, inbreeding within population make the admixed DNA segments smaller with successive generations.
Geneticists studying the size of admixture in current population can not only determine while population groups interacted in history but also the historical timeline of interaction.
The genetic studies of population admixture have revealed information that supports many historical accounts while they undermine still many more. One of the most important theories to be bolstered by population genetics is origin of Indo-European people from the Kurgan culture in the step plains between the Black Sea and the Caspian Sea. Studies show that massive population movement from the Kurgan culture during the early Bronze Age (3000 -2000 BC) changed the demography of lands as far away as in Central and Western Europe, the Middle East and Central Asia, and the Indian sub-continent. It also supports that, despite furious protestations from Hindutva nationalists, the so-called Aryan people are not indigenous to India but migrants from a distant land and culture.
Genetic studies have also shown that around 2000 BC, the Indian sub-continent had two major and very distinctly separate people in their genetic makeup, Ancestral South Indians (ASI) and Ancestral North Indians (ANI) or the descendants of Indo-Europeans. From 2000 BC to until roughly the beginning of the Common Era, there was so much admixing between the ANI and ASI that no population group in India remained free of such mixture. But roughly 1,900 years ago, admixing between populations stopped and no significant interbreeding took place since then. This suggests that the caste system solidified around that time and made exogamy a strict taboo.
Studies have also found that the Middle Eastern and North African populations have significant admixture from sub-Saharan Africa that were inserted between the period from 650 to 1900 AD. This suggests that the rise of Muslim empires in these areas also gave vigorous stimulation to the African slave trade. It is very telling that the lowest amount of African admixture is found among the Druse sect of eastern Mediterranean, a sect that banned slavery and also practiced strict endogamy.
A few analyses of genetic admixture of contemporary Bangladeshis have shown some interesting patterns too. For a people residing in the demographic mélange of South Asia, current Bangladeshi population of the plane lands show remarkable homogeneity in genetic makeup. The population shows a consistent admixture from Austro Asiatic and Dai people of East and South-east Asia that occurred roughly a thousand years ago and also shows a consistent component of admixture from West Asia.
The admixture patterns bolster the argument of Richard Eaton, that until a thousand years ago, East Bengal was a sparsely populated land and the later rapid population increase in the deltaic plains was based on a relative small group of people.